Method for replacing a nitrous oxide based oxidation process with a nitric oxide based oxidation process for substrate processing

ABSTRACT

A method for performing an oxidation process on a plurality of substrates in a batch processing system. According to one embodiment, the method includes selecting a N 2 O-based oxidation process for the substrates including a first process gas containing N 2 O that thermally decomposes in a process chamber of the batch processing system to N 2 , O 2 , and NO byproducts, and generating a replacement NO-based oxidation process for the substrates including a second process gas containing N 2 , O 2 , and NO with molar concentrations that mimic that of the N 2 , O 2 , and NO byproducts in the N 2 O-based oxidation process. According to another embodiment of the invention, the NO-based oxidation process contains NO, O 2 , and an inert gas.

FIELD OF THE INVENTION

The present invention relates to semiconductor substrate processing and,more particularly, to a method for replacing a nitrous oxide-based(N₂O-based) oxidation process used with a nitric oxide-based (NO-based)oxidation process.

BACKGROUND OF THE INVENTION

In the formation of integrated circuits on the surface of asemiconductor substrate, oxide or oxynitride layers are frequently grownor deposited over the surface of a crystalline substrate such assilicon. Oxide or oxynitride layers may have superior electricalproperties, including high electron mobility and low electron trapdensities, that are desirable for device operation in semiconductorapplications. Several methods have been developed for forming oxide andoxynitride layers for semiconductor applications and, followingformation of these layers on a substrate, oxide and oxynitride layersare frequently annealed in to further improve their material andelectrical properties.

In one example, a thin oxide layer may be annealed in the presence of anitrogen-containing gas, such as nitrous oxide (N₂O), at predeterminedprocessing conditions to form an oxynitride layer by nitrogenincorporation from the gas into the oxide layer. In another example, anoxynitride layer may be formed on a substrate by annealing a cleansubstrate in the presence of a N₂O gas. However, one serious shortcomingassociated with using a N₂O gas for oxide annealing and nitrogenincorporation is tool-to-tool variability among similar or dissimilarprocessing tools and processing tool configurations. Tool-to-toolvariability can result in unacceptable thickness variations anddifferent nitrogen depth profiles in the oxynitride layers. In otherwords, processing tool A may have different process results as comparedto processing tool B, even if the same N₂O oxidation process recipe andhardware configuration are used.

Potential solutions to these shortcomings associated with N₂O annealinginclude tighter control on hardware design and manufacturing, inparticular with respect to quartz system components commonly used inbatch processing tools. However, this is an expensive and impracticaloption because quartz system components are often manufactured by hand.

There is thus a need for new methods that reduce or eliminate these andother shortcomings and disadvantages associated with N₂O-based oxidationprocesses.

SUMMARY OF THE INVENTION

Generally, a method is provided for performing an oxidation process on aplurality of substrates in a batch processing system. In particular, amethod is provided for replacing a N₂O-based oxidation process used forsubstrate processing with a NO-based oxidation process. According to oneembodiment of the invention, a N₂O-based oxidation process may beselected and a replacement NO-based oxidation process determined bychemical modeling or by direct measurements of the byproducts of theN₂O-based oxidation process in the process chamber, or by comparingoxidation results of N₂O-based and NO-based oxidation processes.

According to one embodiment of the invention, the method includesselecting a N₂O-based oxidation process including a first process gascontaining N₂O that thermally decomposes in a process chamber of thebatch processing system to N₂, O₂, and NO byproducts, and generating areplacement NO-based oxidation process including a second process gascontaining N₂, O₂, and NO with molar concentrations that mimic that ofthe N₂, O₂, and NO byproducts in the N₂O-based oxidation process. Themethod may further include placing a plurality of substrates in aprocess chamber of the batch processing system, and performing theNO-based oxidation process on the plurality of substrates by introducingthe second process gas into the process chamber.

According to another embodiment of the invention, the method includesselecting a N₂O-based oxidation process including a first process gascontaining N₂O that thermally decomposes in a process chamber of thebatch processing system to N₂, O₂, and NO byproducts, and generating areplacement NO-based oxidation process including a second process gascontaining NO, O₂, and a dilution gas, where the molar concentrations ofNO and O₂ in the second process gas mimic that of the N₂O-basedoxidation process. The method may further include placing a plurality ofsubstrates in a process chamber of the batch processing system, andperforming the NO-based oxidation process on the plurality of substratesby introducing the second process gas into the process chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the invention and,together with a general description of the invention given above, andthe detailed description given below, serve to explain the invention.

FIG. 1 schematically shows a cross-sectional view of a batch processingsystem configured to process plurality of substrates according to anembodiment of the invention;

FIG. 2 shows mole fractions of byproducts from thermal decomposition ofan undiluted N₂O process gas in a process chamber according to anembodiment of the invention;

FIG. 3A shows NO molar concentrations in a process chamber for N₂O-basedand NO-based process gases according to an embodiment of the invention;

FIG. 3B shows O₂ molar concentrations in a process chamber for N₂O-basedand NO-based process gases according to an embodiment of the invention;

FIG. 4A shows O₂/NO molar ratios in a process chamber for N₂O-based andNO-based process gases according to an embodiment of the invention;

FIG. 4B shows gas temperature in a process chamber for N₂O-based andNO-based process gases according to an embodiment of the invention;

FIG. 5A compares base oxide thickness of a N₂O-based oxidation processto different NO-based oxidation processes according to an embodiment ofthe invention;

FIG. 5B compares reoxidation thickness of a N₂O-based oxidation processto different NO-based oxidation processes according to an embodiment ofthe invention; and

FIG. 6 is a process flow diagram of a method for performing an oxidationprocess on a plurality of substrates according to an embodiment of theinvention; and

FIG. 7 is a process flow diagram of a method for performing an oxidationprocess on a plurality of substrates according to another embodiment ofthe invention.

DETAILED DESCRIPTION

Embodiments of the present invention relate to semiconductor substrateprocessing, and more particularly, to a method for replacing a nitrousoxide (N₂O)-based oxidation process used for substrate processing with anitric oxide (NO)-based oxidation process. As used herein, a N₂O-based(NO-based) oxidation process refers to a process of flowing a processgas containing N₂O (NO) into a process chamber containing a plurality ofsubstrates to be processed. The substrate processing can include formingan oxynitride layer on the substrate or performing a reoxidation processon a substrate containing an oxide or oxynitride layer formed thereon.

In a N₂O-based oxidation process, a process gas containing N₂O is flowedinto a heated process chamber. The N₂O thermally decomposes in theprocess chamber into N₂, O₂, and NO byproducts (reaction products) thatprovide the oxidation environment for the plurality of substrates in theprocess chamber exposed to the byproducts. However, the relativeconcentrations of the byproducts in the process chamber, and hence theoxidation environment and the resulting oxynitride layer thickness andcomposition profile, is strongly influenced by several factors,including the concentration of the N₂O gas in the process gas (e.g.,undiluted N₂O or diluted N₂O), the process gas flow rate, the gasresidence time and the gas temperature in the process chamber, positionof substrates in the process chamber, and the physical dimensions andconfiguration of the process chamber. This is due to the highlyexothermic nature of the thermal decomposition of N₂O gas intobyproducts that include N₂, O₂, and NO. This difference in the oxidationenvironment results in tool-to-tool variability among similar ordissimilar processing tools and processing tool configurations and canresult in unacceptable variations in the resulting oxynitride layerthickness and the nitrogen depth profile within the oxynitride layer.

As described above, new oxidation processes are needed that reduce oreliminate the above-mentioned shortcomings associated with N₂O-basedoxidation processing. The present invention is premised on therealization that for a predetermined N₂O-based oxidation process(recipe), an equivalent NO-based oxidation process exists and may beused to reduce or eliminate many of the above-mentioned drawbacksassociated with a N₂O-based oxidation process.

According to one embodiment, the method includes selecting a N₂O-basedoxidation process including a first process gas containing N₂O thatthermally decomposes in a process chamber of the batch processing systemto N₂, O₂, and NO byproducts, and generating a replacement NO-basedoxidation process including a second process gas containing N₂, O₂, andNO with molar concentrations that mimic (i.e., copy or closely resemble;are substantially identical to) the molar concentrations of the N₂, O₂,and NO byproducts in the N₂O-based oxidation process. The method mayfurther include placing a plurality of substrates in a process chamberof the batch processing system, and performing the NO-based oxidationprocess on the plurality of substrates by introducing the second processgas into the process chamber.

According to another embodiment, the method includes selecting aN₂O-based oxidation process including a first process gas containing N₂Othat thermally decomposes thermally decomposes in a process chamber ofthe batch processing system to N₂, O₂, and NO byproducts, generating areplacement NO-based oxidation process comprising a second process gascontaining NO, O₂, and a dilution gas, wherein the molar concentrationsof NO and O₂ in the second process gas mimic that of the N₂O-basedoxidation process. The method may further include placing a plurality ofsubstrates in a process chamber of the batch processing system; andperforming the NO-based oxidation process on the plurality of substratesby introducing the second process gas into the process chamber. Thedilution gas can include at least one of N₂ or Ar. According to oneembodiment of the invention, the first process gas consists of N₂O.According to another embodiment of the invention, the first process gasincludes N₂O and at least one of N₂, O₂, or Ar.

N₂O-based process gases have certain disadvantages in comparison withNO-based oxidation processes. In particular, NO production from N₂Odecomposition is dependent on gas temperature and, thus, thecharacteristics of the gas injection. Therefore, if the method of gasinjection varies or if injector differences exist between tools, the NOconcentration will also vary in the process chambers of the tools. Forcomparison, NO-based oxidation processes are relatively insensitive tohardware variability and can be used to mimic N₂O-based oxidationresults with less consideration to hardware design or injection method.

According to one embodiment of the invention, a N₂O-based oxidationprocess may be selected and the equivalent replacement NO-basedoxidation process may be determined by chemical modeling or by directmeasurement of the byproducts of the N₂O-based oxidation process in theprocess chamber, or by comparing oxidation results of N₂O-based andNO-based oxidation processes.

Chemical modeling of different N₂O-based oxidation processes in aprocess chamber of a batch processing system was performed using asubset of a combustion chemical model from Gas Research Institute, 8600West Bryn Mawr Avenue, Chicago, Ill. The GRI-Mech Version 3.0 naturalgas combustion software (available athttp://www.me.berkeley.edu/gri_mech) is an optimized chemical reactionmechanism capable of representing, among others, natural gas flameprofiles and ignition profiles. Thermal decomposition of N₂O is highlyexothermic and resembles that of flame dynamics, for example H₂/O₂ flamedynamics.

The chemical model subset included the 8 reversible equations listedbelow:2O+M⇄O₂+MN+NO⇄N₂+ON+O₂⇄NO+ON₂O+O₂⇄N₂+O₂N₂O+O⇄2NON₂O(+M)⇄N₂+O(+M)NO+O+M⇄NO₂+MNO₂+O⇄NO+O₂

where M represents a moderator, otherwise known as a third body, which,when present, may effect a change in the reaction rate of one of theabove reactions.

FIG. 1 schematically shows a cross-sectional view of a batch processingsystem configured to process a plurality of substrates according to anembodiment of the invention. The configuration of the batch processingsystem 10 was utilized to chemically model the byproduct distribution inthe process chamber (tube) 12 for different N₂O-based oxidationprocesses containing different N₂O-based process gases. For purposes ofthe modeling, the process chamber 12 was 108 cm in length with an innerdiameter of 273 mm for processing 200 mm diameter substrates (wafers).

The chemical modeling included flowing a N₂O-based process gas into theprocess chamber 12 using a gas injector 18 positioned about 1 cm fromthe gas injection end of the process chamber 12. Although not a part ofthe chemical modeling, a substrate holder 14 configured to support aplurality of wafers 16 is depicted at a typical position in the processchamber 12. The wafers 16 are positioned at a distance between 8 cm and79 cm from the gas injection end of the process chamber 12. In FIG. 1,the substrate holder 14 is configured to support 138 wafers having thatare spaced 5.2 mm apart. The processing conditions used in the chemicalmodeling included a process chamber temperature of 900° C. and a processgas pressure of 615 Torr in the process chamber 12. FIG. 1 further showsfour heater zones for heating the process chamber 12 to thepredetermined process temperature.

FIG. 2 shows mole fractions of byproducts from thermal decomposition ofan undiluted N₂O process gas in a process chamber according to anembodiment of the invention. The mole fractions are plotted as afunction of the distance from the gas injector 18 in the process chamber12 (FIG. 1). The chemical modeling results shown in FIG. 2 correspond tobyproducts of a process gas consisting of a 10 slm N₂O. FIG. 2 showsthat thermal decomposition of N₂O in the process chamber primarilyyields N₂, O₂, and NO byproducts. In fact, the combined amount of N₂,O₂, and NO accounts for the vast majority (99.96%) of the byproductsformed. Minor byproducts from the thermal decomposition of N₂O includeNO₂ and O but, because of their very low mole fractions in the processchamber, these minor byproducts are not thought to significantlycontribute to a substrate oxidation process and, therefore, were notconsidered further. The results in FIG. 2 indicate that thermaldecomposition of a process gas consisting of 10 slm N₂O yields theequivalent of 6.56 slm N₂, 3.23 slm O₂, and 0.203 slm NO in the processchamber 12.

The chemical modeling described above was further utilized to calculateNO molar concentrations (FIG. 3A), O₂ molar concentration (FIG. 3B),O₂/NO molar ratio (FIG. 4A), and gas temperature (FIG. 4B) as a functionof the distance from the gas injection end of the process chamber 12(FIG. 1) for four N₂O-based process gases and one NO-based process gas.The N₂O-based process gases included 1) 10 slm N₂O, 2) 5 slm N₂O, 3) 5Slm N₂O +5 slm N₂, and 4) 5 slm N₂O+5 slm N₂+5 slm O₂. The NO-basedprocess gas included 6.6 slm N₂+3.3 slm O₂+0.21 slm O₂.

FIG. 3A shows NO molar concentrations in a process chamber for N₂O-basedand NO-based process gases according to an embodiment of the invention.Also depicted are the gas injection point and a typical position of asubstrate holder configured for supporting a plurality of wafers duringprocessing. FIG. 3A shows that a process gas consisting of 10 slm N₂Oyielded a NO molar concentration that peaks at about 8.5% near the gasinjection point but reached a steady state NO molar concentration ofabout 2% at a distance of about 8 cm from the gas injection point.Furthermore, a process gas consisting of 5 slm N₂O yielded a NO molarconcentration that peaks at about 7.5% near the gas injection point butreached a steady state concentration of about 5.5% at a distance ofabout 8 cm from the gas injection point.

The chemical modeling results in FIG. 3A demonstrate the highlyexothermic nature of the N₂O thermal decomposition reaction and how therelative N₂O gas flow (10 slm vs. 5 slm) through the process chamber cansignificantly affect the NO molar concentration and, thus, the oxidationenvironment in the process chamber. In this example, a lower N₂O flowyielded a lower peak NO molar concentration but higher steady state NOmolar concentration. Furthermore, a process gas containing N₂O dilutedwith N₂ (5 slm N₂O+5 slm N₂) yielded a steady state NO molarconcentration of about 5.5%, but without the significant peak near thegas injection point that was observed for the undiluted N₂O processgases described above. In addition, a process gas containing N₂O dilutedwith N₂ and O₂ (5 slm N₂O+5 slm N₂+5 slm O₂) yielded a similar NO molarconcentration profile as the process gas containing N₂O diluted with N₂.In FIG. 3A, the composition of the NO-based process gas containing N₂,O₂, and NO (6.6 slm N₂+3.3 slm O₂+0.21 slm O₂) was chosen to mimic theN₂O byproducts described in FIG. 1 for a process gas of 10 slm N₂O.

FIG. 3B shows O₂ molar concentrations in a process chamber for N₂O-basedand NO-based process gases according to an embodiment of the invention.FIG. 3B shows that a process gas consisting of 10 slm N₂O yielded a O₂molar concentration that varied from about 29% near the gas injectionpoint but reached a steady state O₂ molar concentration of about 32% ata distance of about 8 cm from the gas injection point. Furthermore, aprocess gas consisting of 5 slm N₂O yielded an O₂ molar concentrationthat varied from about 29% near the gas injection point but reached asteady state concentration of about 30.5% at a distance of about 8 cmfrom the gas injection point. In this example, a lower N₂O flow yieldeda similar O₂ molar concentration near the gas injection point but adifferent steady state O₂ molar concentration. Furthermore, a processgas containing N₂O diluted with N₂ (5 slm N₂O+5 slm N₂) yielded a steadystate O₂ molar concentration of only about 17%. In addition, a processgas containing N₂O diluted with N₂ and O₂ (5 slm N₂O+5 slm N₂+5 slm O₂)yielded an molar concentration of about 31%.

FIG. 4A shows O₂/NO molar ratios in a process chamber for N₂O-based andNO-based process gases according to an embodiment of the invention. TheO₂/NO molar ratios were determined from the NO molar concentration datain FIG. 3A and the corresponding O₂ molar concentration data in FIG. 3B,respectively. FIG. 4A shows that the O₂/NO molar ratio of the NO-basedprocess gas mimics the O₂/NO molar ratio of 10 slm N₂O under steadystate conditions.

FIG. 4B shows gas temperature in a process chamber for N₂O-based andNO-based process gases according to an embodiment of the invention. Theresults in FIG. 4B show that the gas temperature T in the processchamber for the different N₂O-based and NO-based process gas proceeds asT(10 slm N₂O)>T(5 slm N₂O)>T(5 slm N₂O+5 slm N₂)˜T(5 slm N₂O+3.25 slmN₂+1.75 slm O₂)>T(6.6 slm N₂+3.3 slm O₂+0.21 slm NO). The results inFIG. 4B demonstrate that the gas temperature, and thus the oxidationenvironment, is highly dependant on the N₂O-based process gascomposition and the process gas flow. In particular, a gas temperatureas high as about 1900° C. is calculated for 10 slm N₂O, about 1700° C.for 10 slm N₂O, and about 1350° C. for 5 slm N₂O+5 slm N₂ and 5 slmN₂O+3.25 slm N₂+1.75 slm O₂. In comparison, the gas temperature of theNO-based process gas is much lower than the NO₂-based process gas (i.e.,from about 600° C. to about 800° C.).

As shown in FIGS. 3A and 3B, a N₂O-based process gas consisting of a N₂Oflow of 10 slm can be replaced by an equivalent NO-based process gascontaining 6.6 slm N₂+3.3 slm O₂+0.21 slm NO. Although not shown inFIGS. 3A and 3B, it is apparent that a N₂O-based process gas consistingof a N₂O flow of 5 slm can be replaced by an equivalent NO-based processgas containing 3.2 slm N₂+1.52 slm O₂+0.28 slm NO.

Table 1 summarizes the results of FIGS. 3A, 3B, and 4A. Table 1 showsthe equivalent N₂, O₂, and NO molar concentrations for each of the fourN₂O-based process gases and the NO-based process gas. For example, aprocess gas consisting of 10 slm N₂O thermally decomposes to 66% (6.6slm) N₂, 32% (3.2 slm) O₂, and 2% (0.2 slm) NO. TABLE 1 Process gas(slm) N₂ O₂ NO 10 slm N₂O 66% (6.6 slm) 32% (3.2 slm)  2% (0.2 slm) 5slm N₂O 64% (3.2 slm) 30.5% (1.52 slm)  5.5% (0.28 slm) 5 slm N₂O +77.5% (7.75 slm)  17% (1.7 slm)  5.5% (0.55 slm) 5 slm N₂ 5 slm N₂O +63.5% (6.35 slm)  31% (1.52 slm) 5.5% (0.55 slm) 3.25 slm N₂ + 1.75 slmO₂ 6.6 slm N₂ + 65% (6.6 slm) 33% (3.3 slm)   2% (0.21 slm) 3.3 slm N₂ +0.21 slm NO

In summary, the chemical modeling results presented in FIGS. 2-4Bdemonstrate that N₂O thermal decomposition yields N₂, O₂, and NObyproducts with an important composition gradient and decompositiontemperature (gas temperature) gradient along a significant portion ofthe length of the process chamber. Furthermore, the relativeconcentrations of the N₂, O₂, and NO byproducts are a function of N₂Ogas flow, N₂O concentration in the process gas, and the gas temperature.This explains the tool-to-tool variability. Furthermore, the chemicalmodeling demonstrates that an equivalent NO-based process gas containingN₂, O₂, and NO gas may be selected for each N₂O-based process gas andthat the molar concentrations of O₂ and NO in the NO-based process gasis only weakly dependant on system design.

According to another embodiment of the invention, direct measurement ofthe byproducts of the N₂O-based oxidation process in the process chambermay be utilized to generate an equivalent NO-based oxidation process. Inone example, the molar concentrations of N₂, O₂, and NO byproducts inthe gaseous environment in the process chamber may be measured by massspectroscopy, by light absorption, or by light emission techniques.These analytical techniques are well known to those skilled in the art.

According to another embodiment of the invention, a NO-based oxidationprocess to replace a N₂O-based oxidation process may be determined byperforming oxidation processes on substrates using N₂O-based andNO-based oxidation processes, and subsequently comparing the oxidationresults. The oxidation processes may include forming a base oxynitridelayer on a substrate or performing a reoxidation process on a substratecontaining an oxide or oxynitride layer formed thereon.

In the example shown in Table 2, different NO-based process gasescontaining N₂, O₂, and NO were utilized in oxidation processes andcompared to that of a process gas consisting of 5 slm N₂O. The oxidationprocess conditions included a process chamber temperature of 900° C., aprocess gas pressure of 615 Torr in the process chamber, and a 15 minuteexposure time. TABLE 2 NO O₂ N₂ Time (slm) (slm) (slm) (min) O₂/NO NO %O₂ % 0.15 1.6 3.25 15 10.67 3 32 0.20 1.6 3.20 15 8.00 4 32 0.25 1.63.15 15 6.40 5 32 0.30 1.6 3.10 15 5.33 6 32 0.35 1.6 3.05 15 4.57 7 32N₂O = 5 15

FIG. 5A compares base oxide thickness of a N₂O-based oxidation processto different NO-based oxidation processes according to an embodiment ofthe invention. FIG. 5A shows that the base oxide thickness using a 5 slmN₂O process gas was closely approximated by a NO-based process gascontaining about 5.25% molar concentration of NO, 32% concentration ofO₂, and balance N₂. FIG. 5B compares reoxidation thickness of aN₂O-based oxidation process to different NO-based oxidation processesaccording to an embodiment of the invention. The reoxidation process wasperformed by exposing oxynitride films formed by N₂O-based oxidation andNO-based oxidation to an O₂ ambient at a pressure of one atmosphere for30 min. Then, the resulting films thickness was measured again and thereoxidation thickness increase calculated and plotted in FIG. 5B. Thereoxidation thickness increase is directly proportional to the amount ofnitrogen at the interface of the oxynitride film and the substrate.

FIGS. 5A and 5B shows that the base oxide thickness and the reoxidationthickness increase using a 5 slm N₂O process gas was closelyapproximated by a NO-based process gas containing about 5.25% and about5.5% molar concentration of NO, respectively. This is also goodagreement with the results of the chemical modeling results from FIGS.3A and 3B, where a 5 slm N₂O process gas yielded about 5.5% steady statemolar concentration of NO and about 32% steady state molar concentrationof O₂. Therefore, the chemical modeling agrees well with tool datadisplayed in FIGS. 5A and 5B.

FIG. 6 is a process flow diagram of a method for performing an oxidationprocess on a plurality of substrates according to an embodiment of theinvention. The process 600 includes, in step 602, selecting an N₂O-basedoxidation process including a first process gas containing N₂O thatthermally decomposes to N₂, O₂, and NO byproducts. According to oneembodiment of the invention, the N₂O-based process gas containsundiluted N₂O gas.

In step 604, a replacement NO-based oxidation process is generated thatincludes a second process gas containing N₂, O₂, and NO with molarconcentrations that mimic that of the N₂, O₂, and NO byproducts in theN₂O-based oxidation process. According to one embodiment of theinvention, the second process gas may include 1%-10% NO, 10%-50% O₂, andbalance N₂. According to another embodiment of the invention, secondprocess gas may include 1%-3% NO, 20%-40% O₂, and balance N₂.

In step 606, a plurality of substrates is provided in a process chamberof a batch processing system. The substrates can be clean of any oxidelayer, or alternately, the substrates can contain a base oxide oroxynitride layer. The batch processing system can, for example, processsubstrates of any size, such as 200 mm substrates, 300 mm substrates, oreven larger substrates. Furthermore, the processing system cansimultaneously process up to about 200 substrates, or more.Alternatively, the processing system can simultaneously process up toabout 25 substrates.

In step 608, a NO-based oxidation process is performed on the pluralityof substrates by introducing the second process gas into the chamber.The oxidation process can form an oxynitride layer on clean substrates,or alternately, the oxidation process can be a reoxidation processperformed on oxide or oxynitride layers. For example, the processconditions can include a process chamber temperature between about 600°C. and about 1000° C., and a process chamber pressure between about 100mtorr and about 650 Torr.

FIG. 7 is a process flow diagram of a method for performing an oxidationprocess on a plurality of substrates according to another embodiment ofthe invention. The process 700 includes, in step 702, selecting anN₂O-based oxidation process including a first process gas containing N₂Othat thermally decomposes to N₂, O₂, and NO byproducts. According to oneembodiment of the invention, the first process gas contains undilutedN₂O gas. According to another embodiment of the invention, the firstprocess gas contains N₂O gas and at least one of N₂ or O₂.

In step 704, a replacement NO-based oxidation process is generated thatincludes a second process gas containing NO, O₂, and a dilution gas,wherein the molar concentrations of NO and O₂ in the second process gasmimic that of the N₂O-based oxidation process. According to oneembodiment of the invention, the first process gas contains undilutedN₂O gas. According to another embodiment of the invention, the firstprocess gas contains N₂O gas and at least one of N₂, O₂, or Ar.According to an embodiment of the invention, the dilution gas cancontain Ar. According to one embodiment of the invention, the secondprocess gas can include 1%-10% NO, 10%-50% O₂, and balance dilution gas.According to another embodiment of the invention, second process gas caninclude 1%-3% NO, 20%-40% O₂, and balance dilution gas. The dilution gascan contain at least one of N₂ or Ar.

In step 706, a plurality of substrates is provided in a process chamberof a batch processing system. The substrates can be clean of any oxidelayer, or alternately, the substrates can contain a base oxide oroxynitride layer.

In step 708, a NO-based oxidation process is performed on the pluralityof substrates by introducing the second process gas into the chamber.The oxidation process can form an oxynitride layer on clean substrates,or alternately, the oxidation process can be a reoxidation processperformed on oxide or oxynitride layers. For example, the processconditions can include a process chamber temperature between about 600°C. and about 1000° C., and a process chamber pressure between about 100mtorr and about 650 Torr.

Process gas delivery and cost comparison between N₂O-based and NO-basedoxidation processes show that NO gas delivery is slightly more difficultthan N₂O gas due to the more corrosive nature of NO and NO gas is moreexpensive (currently ˜4.9×) than N₂O gas. However, when replacing an N₂Ogas with NO gas, the actual cost of the NO gas is much lower than thatof N₂O since proportionally much less NO gas is used than N₂O gas. Forexample, a 10 slm N₂O process gas flow may be replaced by a NO-basedprocess gas containing 2% NO. In another example, 5 slm N₂O process gasflow may be replaced by a NO-based process gas containing 5.5% NO.

While the present invention has been illustrated by the description ofone or more embodiments thereof, and while the embodiments have beendescribed in considerable detail, they are not intended to restrict orin any way limit the scope of the appended claims to such detail.Additional advantages and modifications will readily appear to thoseskilled in the art. The invention in its broader aspects is thereforenot limited to the specific details, representative apparatus and methodand illustrative examples shown and described. Accordingly, departuresmay be made from such details without departing from the scope of thegeneral inventive concept.

1. A method for processing a plurality of substrates in a batchprocessing system, the method comprising: selecting a N₂O-basedoxidation process for the substrates comprising a first process gascontaining N₂O that thermally decomposes in a process chamber of thebatch processing system to N₂, O₂, and NO byproducts; and generating areplacement NO-based oxidation process for the substrates comprising asecond process gas containing N₂, O₂, and NO with molar concentrationsthat mimic that of the N₂, O₂, and NO byproducts in the N₂O-basedoxidation process.
 2. The method according to claim 1, whereingenerating the replacement NO-based oxidation process further comprises:determining molar concentrations of the NO, O₂, and N₂ byproducts fromthe thermal decomposition of the first process gas in the processchamber; and forming the second process gas based on the determinedmolar concentrations.
 3. The method according to claim 2, whereindetermining the molar concentrations comprises: calculating by chemicalmodeling molar concentrations of the NO, O₂, and N₂ byproducts in theprocess chamber.
 4. The method according to claim 2, wherein determiningthe molar concentrations comprises: analytically measuring molarconcentrations of the NO, O₂, and N₂ byproducts in the process chamber.5. The method according to claim 2, wherein determining the molarconcentrations comprises: performing a N₂O-based oxidation processyielding a first substrate oxidation or reoxidation thickness;performing a plurality of NO-based oxidation processes using differentmolar concentrations of NO, O₂, and N₂ in the process chamber eachyielding a second substrate oxidation or reoxidation thickness; andselecting the replacement NO-based oxidation process by comparing thefirst and second substrate oxidation or reoxidation thicknesses of theN₂O-based and NO-based oxidation processes.
 6. The method according toclaim 1, wherein the second process gas comprise 1%-10% NO, 10%-50% O₂,and balance N₂.
 7. The method according to claim 1, wherein the secondprocess gas comprises 1%-3% NO, 20%-40% O₂, and balance N₂.
 8. Themethod according to claim 1, wherein selecting the N₂O-based oxidationprocess further comprises: choosing a composition of the first processgas, a gas flow rate of the first process gas, a process chamberpressure, and a process chamber temperature.
 9. The method according toclaim 1, further comprising: placing the substrates in the processchamber of the batch processing system; and performing the NO-basedoxidation process on the substrates by introducing the second processgas into the process chamber.
 10. A method for processing a plurality ofsubstrates in a batch processing system, the method comprising:selecting a N₂O-based oxidation process for the substrates comprising afirst process gas containing N₂O that thermally decomposes in a processchamber of the batch processing system to N₂, O₂, and NO byproducts; andgenerating a replacement NO-based oxidation process for the substratescomprising a second process gas containing NO, O₂, and a dilution gas,wherein the molar concentrations of NO and O₂ in the second process gasmimic that of the N₂O-based oxidation process.
 11. The method accordingto claim 10, wherein the first process gas comprises undiluted N₂O. 12.The method according to claim 10, wherein the first process gascomprises a mixture of N₂O and at least one of N₂, O₂, or Ar.
 13. Themethod according to claim 10, wherein the dilution gas comprises atleast one of N₂ or Ar.
 14. The method according to claim 10, whereingenerating the replacement NO-based oxidation process comprises:determining molar concentrations of the NO, O₂, and N₂ byproducts fromthe thermal decomposition of the first process gas in the processchamber; and forming the second process gas based on the determinedmolar concentrations.
 15. The method according to claim 14, whereindetermining the molar concentrations comprises: calculating by chemicalmodeling molar concentrations of the NO, O₂, and N₂ byproducts in theprocess chamber.
 16. The method according to claim 14, whereindetermining the molar concentrations comprises: analytically measuringmolar concentrations of the NO, O₂, and N₂ byproducts in the processchamber.
 17. The method according to claim 14, wherein determining themolar concentrations comprises: performing a N₂O-based oxidation processyielding a first substrate oxidation or reoxidation thickness;performing a plurality of NO-based oxidation processes using differentmolar concentrations of NO, O₂, and the dilution gas in the processchamber each yielding a second substrate oxidation or reoxidationthickness; and selecting the replacement NO-based oxidation process bycomparing the first and second substrate oxidation or reoxidationthicknesses of the N₂O-based and NO-based oxidation processes.
 18. Themethod according to claim 10, wherein the second process gas comprises1%-10% NO, 10%-50% O₂, and balance the dilution gas.
 19. The methodaccording to claim 10, wherein the second process gas comprises 1%-3%NO, 20%-40% O₂, and balance the dilution gas.
 20. The method accordingto 10, wherein selecting the N₂O-based oxidation process furthercomprises: choosing a composition of the first process gas, a gas flowrate of the first process gas, a process chamber pressure, and a processchamber temperature.
 21. The method according to claim 10, furthercomprising: placing the substrates in the process chamber of the batchprocessing system; and performing the NO-based oxidation process on thesubstrates by introducing the second process gas into the processchamber.